July 26, 2018

Preconfiguration, quasi-static time series, and autonomous operation are all features
contributing to the expansion of distributed energy systems, thanks to advanced inverters
and an NREL- and Sacramento Municipal Utility District (SMUD)-developed platform called
PRECISE.

PRECISE, a tool that allows the preconfiguration of advanced inverter settings, can
dramatically reduce the time it takes to receive approval to install and connect rooftop
solar onto a utility's distribution feeder. Photo by Dennis Schroeder

The tool, PREconfiguring and Controlling Inverter SEtpoints (PRECISE), is a technology
that evolved from NREL’s work at the Energy Systems Integration Facility (ESIF) with
Hawaiian Electric Companies (HECO), inspired by the surge in customer interest to connect home-installed solar to Hawaii’s
grid. Like HECO, SMUD began to see a surplus in solar photovoltaic (PV) interconnection
applications from residents in Sacramento in 2016, challenging the utility’s ability
to respond to each request in a timely manner while considering voltage control and
grid reliability.

During this time, and as an outgrowth of the inverter studies performed in Hawaii,
NREL Engineer Adarsh Nagarajan had been exploring the idea of preconfiguring advanced
inverters based on residents’ locations, clusters, and seasonal weather patterns.

“I realized we could assume that even if an inverter has communications, we are not
really trying to communicate with it every 10-15 minutes,” said Nagarajan. “We could
preconfigure the inverter and set modes for seasons. Then it would be done before
it’s even installed. You turn on the inverter, and it knows what to do.”

With support from SMUD, Nagarajan and the PRECISE team began developing a planning
and real-time operation platform that would enable distribution utilities to identify
optimal inverter modes and settings, ultimately to maximize the cost-effective use
of installed PV systems. The team found that the tool can dramatically reduce the
time it takes to receive approval to install and connect PV systems onto the utility
distribution feeder, from 10-15 days down to 5. PRECISE is now helping the Sacramento
utility—and utilities in India—to seamlessly interconnect and integrate high penetrations
of PV onto today’s grid in a safe, cost-effective, secure, and reliable way.

“The PRECISE platform expands upon our work that involved the quasi-steady state modeling
of Hawaii’s distribution systems,” said Martha Symko-Davies, Laboratory Program Manager
of Energy Systems Integration. “The exciting part of this project is seeing how the
work leverages a technology that we developed in a more automated way, scaling to
other regions in the United States and beyond.”

With PRECISE, as soon as a customer applies for rooftop or ground-mount PV system
installation, a utility operator can identify exactly where the correct feeder is
located based on the customer’s interconnection address. The operator can then use
PRECISE to model the distribution feeder and preconfigure advanced inverter modes
that help provide grid support, enabling seamless interconnection with much less wait
time.

Beyond the United States, this kind of immediate service and fast access is exactly
what’s needed in places like India where some utilities are installing PV systems
at the gigawatt scale.

As Nagarajan explained, solar is booming in India at an extraordinary rate, but distributed
energy in India is still, in a sense, the “Wild West.” Without decades of refinement
to interoperability standards and advanced grid technologies like PRECISE, too much
deployment could lead to reliability concerns. The country’s fast growth in solar—teamed
with the opportunity for PRECISE to add significant value—is why Nagarajan has already
begun discussions with utilities in India about the tool.

“PRECISE can help fast-forward to best practices,” he said. “The utilities in India
are aware of how quickly the industry is changing. They want to provide active power
support. They know that advanced inverters are the way to achieve that, but they aren’t
sure where to start.”

Nagarajan expects that his team will start to model an Indian feeder this August or
September and plans to attend the Distribution Utility Meet in Mumbai this November.
By bringing PRECISE to India, his hope is that the country’s regulation agency will
also gain the benefit of taking the U.S. Institute of Electrical and Electronics Engineers (IEEE) interconnection standard
1547-2018, adopting it to work with their grid infrastructure, and achieving active power support
through advanced inverter standards, pre-configured settings, and greater access to
distributed energy.

“Moving these technologies from West to East is truly a high-impact achievement for
our researchers and partners,” said Symko-Davies, adding that with hardware-in-the-loop
capabilities at the ESIF, she sees the PRECISE platform extending to any region where
there’s opportunity to better manage high penetration PV. “With PRECISE, it will be
much easier for people to integrate their PV onto the grid.”